A fish count in the Animas River on Tuesday found populations have been drastically affected by deadly runoff from the 416 Fire burn scar.
Fish kills because of ash and dirt washing into the river started in mid-July, but a massive rain event around July 17 likely killed most of the fish in the waterway, wildlife officials said at the time.
The dirty runoff lowers the oxygen content in water, suffocating fish, which have been further stressed by abnormally low flows and high water temperatures.
For the first time since the 416 Fire runoff events, wildlife managers with Colorado Parks and Wildlife conducted a fish survey to better understand the extent of the fish kill.
Usually, CPW will use an electrofishing device from a raft to stun fish to survey two 1,000-foot sections of the Animas River: from Durango High School to the Ninth Street Bridge and from Cundiff Park to the High Bridge.
This year, low flows forced wildlife managers to use an electrofishing device from the banks and from in the river.
Jim White, an aquatic biologist for CPW, said in a normal year, a survey will find somewhere around 40 brown trout and 40 rainbow trout in the stretch from Cundiff Park to the High Bridge.
This year, CPW found one brown trout and one rainbow trout in that stretch and no molted sculpin, a small native species of fish that’s a key food source for trout.
In the stretch of river between Durango High School and the Ninth Street Bridge, CPW found four brown trout and two rainbow trout, as well as some molted sculpin, bluehead suckers and speckled dace.
“Normally, we’d catch 10 times that,” White said.
White said Tuesday’s survey presented a good news, bad news scenario for the Animas River.
The good news: There are fish surviving in the river, which means the fish can eventually spawn and recover.
The bad news: The waterway has been severely affected by the 416 Fire debris flows, which will likely pose a risk to aquatic life for years to come.
White said, ideally, the San Juan Mountains will have a good year for snowpack, which in turn, will give the Animas a good spring runoff to wash out the river and lingering sediment.
That will allow native fish, which CPW does not stock, to respawn. Then, CPW can restock trout populations.
“We can work on bringing the trout population back pretty quickly through stocking,” he said.
CPW usually stocks 20,000 rainbow trout fingerlings and 20,000 brown trout fingerlings in the fall, but those plans have been canceled this year because of the river’s poor condition.
CPW will instead hope for a good snowpack this winter, and restock after the spring runoff, White said.
The process of restoring the Animas River to some sense of normalcy could take years, White said.
“The fish are going to bounce back,” he said. “And it’s going to be a combination process of managing those fish back and also naturally having fish come back on their own.”
jromeo@durangoherald.com